This application is based on patent application Ser. No. 11-111495 (1999) filed Apr. 19, 1999 in Japan, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a printing system which conducts printing operation by using coloring materials of a plurality of colors, and more specifically to a printing system equipped with a calibration function, a printing system which can form test patterns in order to detect printing characteristics such as output density balance of each color, an information processing apparatus, and a printing apparatus.
2. Description of Related Art
Multi-media is making a rapid progress nowadays along with the propagation of personal computers and OA (office automation) equipment as well as the development of communication technology. Under such circumstance, there is a tendency that color images are increasingly demanded. As output devices for color images, various printing systems have been developed. For example, there are printers of the ink jet system, the electro-photographic system, and the heat transfer system.
In the case of current printing devices where photograph-like color image output is frequently produced, color images generally use three coloring materials (colorants) of chromatic colors, namely, cyan (C), magenta (M), and yellow (Y) or four coloring materials that include the three chromatic color materials and black (K). However, because of the balance of the output characteristics (reflection density or lightness, i.e. brightness of color or darkness of color, saturation, hue, etc.) among difference printing heads that print each coloring material, it does not necessarily follow that they are suitable for all apparatuses.
For instance, in an ink jet printing device, among printing heads, there are variations in an amount of heat (film thickness) generated by heaters to eject ink, and variations in size (diameter) of ink ejection nozzles, causing differences in the amount of ejected ink among the individual printing heads. There are some cases in which such individual differences give rise to a color deviation (a density deviation). In such cases, a desired image quality cannot be obtained. Thus, in order to compensate for such color deviations, the printing apparatus is equipped with various calibration functions such as xcex3 correction as well as various other color deviation correction means.
In the calibration, a detection pattern is actually printed on predetermined printing media. Data showing color deviation as obtained by detection from such a printing result is used as data to compensate for the color deviation.
As a color deviation detection method based on individual differences among the devices, two methods are actually used. In one method, the detection pattern is detected by using a detection instrument such as a scanner. In the other method, the detection is conducted visually by eye.
Now, the detection method of each of the above-mentioned color deviations will be outlined below.
In the method using an input instrument such as a scanner, for instance, as used in Japanese Patent No. 2661917, a detection pattern is printed for each coloring material (colorant) consisting of C, M, Y, and K, and then, each pattern is read out with a scanner. A deviation between a value thus read out and an expected output value of each detection pattern Is detected. Based on such deviations, the method of correcting the color with xcex3 value is disclosed.
At this time, there is one method in which as a detection pattern to detect the color deviation, a gradation pattern of each elemental color is printed along with a solid pattern of C, M, Y, and K; and not only the color deviation of a single gradation but also output characteristics of intermediate gradation is also detected, thereby improving the accuracy of color deviation. There is another method in which the detection correction accuracy is improved by printing patch patterns of secondary and tertiary colors which combine C, M. Y, and K, individually.
On the other hand, in the method in which visual detection is used, the following method is employed.
Since it is difficult to detect absolute values of the output characteristics of the respective elemental colorants, principally 3 coloring materials of C, M, and Y are mixed. A detection pattern of the tertiary color of this mixture is printed. Color deviations are detected therefrom. More specifically, in the method, a printing pattern formed by using a tertiary color obtained by mixing the coloring materials of C, M, and Y at a ratio where achromatic color is expected when using printing heads each having an average discharge amount printed at a center, a plurality of test pattens having substantially gray color obtained by mixing the coloring materials with a ratio slightly changed are printed around the printing pattern, and then a test pattern which is the closest to the central achromatic color among the test patterns is visually selected. In this way, the output characteristics of each coloring materials of C, M and Y are detected. In other words, this detection method utilizes the fact that the gray color patterns are no longer an achromatic color when an effect of the color material having large output characteristics is caused by a slight deviation in balance of the output characteristics of C, M and Y. If this detection method is used, even in the case of visual detection, color deviation can be detected easily.
With respect to cases in which color deviation detection is conducted by this visual detection method, one example of the detection pattern will be explained using FIG. 11.
In FIG. 11, the detection pattern P shown therein consists of a set of patches (pattern set) composed of a pair of top and bottom frames in contact with each other, with sets more than one (in this case the number is 5) being aligned sideways to thereby constitute P (1, 1) to P (5, 5). In the figure, the four numbers shown in the upper frame and the lower frame inside of each patch represent multi-value gradation levels of C, M, Y, and X from the top. In addition, said upper frames are patch patterns of process black (PCBk) which is made by mixing coloring materials having chromatic colors C, M and Y, and the patch pattern of the lower side is composed of a coloring material of achromatic color, black (K) only. The PCBk of the upper side has Y fixed at a level of 128. Gradation values for C become larger as patches are arranged closer to the right side (i.e., the density becomes higher), and gradation values for M become larger as patches are arranged at the lower side.
As described above, since the patch pattern of PCBk and the patch pattern of Bk are laid out in the above detection pattern, it becomes possible to improve the detection accuracy based on visual detection to a considerable degree. This is a detection method that utilizes visual characteristics of a human being such that even slight color deviations can be detected in the case a plurality of objects are placed adjacent to each other. Hereinafter, this comparison method shall be referred to as the adjacency comparison method.
According to this adjacency comparison method, even if the color difference is at a sufficiently low level of 0.8 to 1.6, it is known that the color difference can be recognized. As a result, in comparison with vaguely selecting a patch that is closest to an achromatic color from among a plurality of PCBk patches, the detection accuracy can be improved significantly. For instance, even in case the color difference is at a sufficiently low level such as 0.8 to 1.6, the detector can recognize the difference reliably. By inputting correction data obtained on the basis of a gradation value of each color material that forms a detection pattern that is closest to black K, calibration is conducted, and a suitable image having no color deviation is obtained.
In the case of the printing apparatus in which the color deviation of the individual apparatus is compensated by said calibration, the suitability of correction data used for the calibration is an important factor in determining the quality of a printed image. Furthermore, if a detection apparatus such as a scanner is used for such detection, a high accuracy color deviation detection becomes possible, and hence, it can be presumed that suitable correction data is obtained. However, actually, it does not mean that all users have detection devices such as scanners. In addition, there are a variety of scanners which differ in capability, characteristics, etc. Thus, there is a possibility that a discrepancy may occur in detection results depending on devices used. Consequently, it does not necessarily follow that suitable calibration takes place.
In contrast, color deviation correction by visual detection is slightly inferior to the detection by means of a scanner from the standpoint of stability or the like, but significant detection accuracy can be expected by using the adjacency comparison method.
However, in the case of recent printing apparatuses, in particular, in ink-jet printers that use colored ink, for the purpose of attaining an improved image quality, printing systems that use Y, M, C ink having a ordinary concentration (high concentration ink) as well as LY, LM, LC ink with the same hues but lower concentration (low concentration ink) are implemented in order to reduce particle-like appearance. In this case, since ink of the same color is collectively subjected to color deviation detection in the conventional adjacency comparison method. If there occurs a deviation in the balance of an ejection amount between a high concentration ink and a low concentration ink, there arises a problem of hampering the color deviation correction. In other words, in the case a high concentration ink and a low concentration ink are used together, there is need to consider not only a density balance among inks of different hues, but also a density balance between high concentration ink and low concentration ink. This point was not considered at all hitherto, and suitable correction data could not be obtained in some cases.
Furthermore, a printing system aiming at an improved image quality by using ink other than Y, M, C, and K, for instance, other ink (special ink) including typically, R, G, and B, is also implemented. However, in the case of such printing apparatus, no color deviation correction is implemented. Currently, there exists no color deviation detection using the adjacency comparison method in particular.
An object of the present invention is to permit optimization of a density balance among coloring materials so that printing free of color deviation can be achieved, in the case of using a plurality of densities for coloring materials having the same color, or in the case of using other coloring material in addition to coloring materials Y, M, C, and K.
In a first aspect of the present invention, there is provided a printing information processing apparatus which conducts processing for printing test patterns used for color deviation correction processing in the printing apparatus by making at least one ordinary coloring material used for the printing apparatus and a special coloring material having a color belonging within a reproducible range based on the ordinary coloring material, the predetermined printing characteristics, respectively, the printing information processing apparatus comprising:
means for forming a plurality of patches, each being formed with a reference area composed of a predetermined single-color within the color reproducible range in the coloring materials used to form the test patterns, and a test area adjacently positioned to the reference area and formed by using at least one the coloring materials;
wherein each of the plurality of patches includes areas in which at least either of the reference area or the test area contains the special coloring materials.
In a second aspect of the present invention, there is provided a printing apparatus which conducts processing for printing test patterns used for color deviation correction processing in the printing apparatus by making at least one ordinary coloring material used for the printing apparatus and a special coloring material having a color belonging within a reproducible range based on the ordinary coloring material, the predetermined printing characteristics, respectively, the printing apparatus comprising:
means for forming a plurality of patches each being formed with a reference area composed of a predetermined single-color within the color reproducible range in the coloring materials used to form the test patterns, and a test area adjacently positioned to the reference area and formed by using at least one the coloring materials;
wherein the plurality of patches each includes areas in which at least either of the reference area or the test area contains the special coloring material.
In a third aspect of the present invention, there is provided a test pattern forming method which conducts processing for printing test patterns used for color deviation correction processing in the printing apparatus by making at least one ordinary coloring material used for the printing apparatus and a special coloring material having a color belonging within a reproducible range based on the ordinary coloring material, the predetermined printing characteristics, respectively, the test pattern forming method comprising:
a step for forming a plurality of patches each being formed with a reference area composed of a predetermined single-color within the color reproducible range in the coloring materials used to form the test patterns, and a test area adjacently positioned to the reference area and formed by using at least one the coloring materials;
wherein the plurality of patches each includes areas in which at least either of the reference area or the test area contains the special coloring material.
In a fourth aspect of the present invention, there is provided a memory media which stores a program readable which conducts processing for printing test patterns used for color deviation correction processing in the printing apparatus by making at least one ordinary coloring material used for the printing apparatus and a special coloring material having a color belonging within a reproducible range based on the ordinary coloring material, the predetermined printing characteristics, respectively, the program comprising:
processing for forming a plurality of patches each being formed with a reference area composed of a predetermined single-color within the color reproducible range in the coloring materials used to form the test patterns, and a test area adjacently positioned to the reference area and formed by using at least one the coloring materials;
wherein the plurality of patches each includes areas in which at least either of the reference area or the test area contains the special coloring material.
In this manner, in the present invention, a test area and a reference area are formed at adjacent positions, and thus, in comparison between the reference area and the test area, good comparison results can be obtained by the Adjacency Comparison Method. In addition, since special coloring material is contained in either of the patterns, even if special coloring material with low frequency of use is contained in the coloring materials, it will be possible to detect density balance between the special coloring material and other ordinary coloring materials as well, and it will be possible to set suitable density balance for all coloring materials.
Therefore, for instance, in the case a plurality of densities are used for the same color coloring material, or in the case low concentration ink CL or CM is used together with ordinary ink such as C, M, Y, or K, suitable density balance can be set for all ink, thereby preventing the occurrence of color deviation in advance.
The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.